Bowen et al., U.S. patent application Ser. No. 07/209,372 filed on Jun. 21, 1988, U.S. Pat. No. 4,918,175 (Apr. 17, 1990), discloses bismuth (phosph/sulf)ated saccharides. In nature and gist, these compositions are bismuth phosphorylated and/or sulfonated saccharides, which are useful as pharmaceuticals in ameliorating disorders associated with gastric mucosal damage. Preparation of the bismuth (phosph/sulf)ated saccharides according to the practice of that invention involves contacting a hydrogen (phosph/sulf)ated saccharide with a bismuth substance. Preparations from metal salts of the (phosph/sulf)ated saccharides, other than bismuth of course, involve, for example, ion exchange procedures with an ion exchange resin such as a sulfonated divinyl benzene in its hydrogen ion form. The metal salt, for example, the potassium salt, is passed over the resin to prepare the hydrogen (phosph/sulf)ated saccharides, which are used for contacting with the bismuth substance, for example, freshly prepared bismuth hydroxide, to prepare the bismuth (phosph/sulf)ated saccharides.
Duff, U.S. patent application Ser. No. 07/351,714 filed on May 15, 1989, abandoned in favor of Ser. No. 07/430,059 filed on Oct. 31, 1989, discloses preparation of hydrogen and bismuth (phosph/sulf)ated saccharides. In summary, that invention, in one aspect, provides a process for preparing a hydrogen (phosph/sulf)ated saccharide comprising contacting a metal salt of a (phosph/sulf)ated saccharide with a water soluble organic acid having a pKa less than the pKa of the hydrogen (phosph/sulf)ated saccharide to be prepared, by steps under conditions such that the hydrogen (phosph/sulf)ated saccharide is prepared. Another aspect provides a process for preparing a bismuth (phosph/sulf)ated saccharide comprising steps of contacting, first, a metal salt of a (phosph-sulf)ated saccharide with a water soluble organic acid having a pKa less than the pKa of a hydrogen (phosph/sulf)ated corresponding to the bismuth (phosph/sulf)ated saccharide to be prepared, and second, the product of said first step with a bismuth substance, by steps under conditions such that the bismuth (phosph/sulf)ated saccharide is prepared.
What is lacking and needed is a process which can prepare hydrogen and/or bismuth (phosph/sulf)ated saccharides, particularly from salts other than of course bismuth, that is simpler and more efficient than, heretofore known. Desirably, the process would be employable with advantage in preparation of large or commercial scale amounts of the product (phosph/sulf)ated saccharide.